getvlc.c

MPEG2视频编解码算法方面的源代码(包括编码和解码)

    {
      Print_Bits(code,3,MVtab0[code].len);
      printf("%d): %d\n",
        Show_Bits(1),Show_Bits(1)?-MVtab0[code].val:MVtab0[code].val);
    }
#endif /* TRACE */

    return Get_Bits1()?-MVtab0[code].val:MVtab0[code].val;
  }

  if (code>=24)
  {
    code >>= 3;
    Flush_Buffer(MVtab1[code].len);

#ifdef TRACE
    if (Trace_Flag)
    {
      Print_Bits(code,6,MVtab1[code].len);
      printf("%d): %d\n",
        Show_Bits(1),Show_Bits(1)?-MVtab1[code].val:MVtab1[code].val);
    }
#endif /* TRACE */

    return Get_Bits1()?-MVtab1[code].val:MVtab1[code].val;
  }

  if ((code-=12)<0)
  {
    if (!Quiet_Flag)
/* HACK */
      printf("Invalid motion_vector code (MBA %d, pic %d)\n", global_MBA, global_pic);
    Fault_Flag=1;
    return 0;
  }

  Flush_Buffer(MVtab2[code].len);

#ifdef TRACE
  if (Trace_Flag)
  {
    Print_Bits(code+12,9,MVtab2[code].len);
    printf("%d): %d\n",
      Show_Bits(1),Show_Bits(1)?-MVtab2[code].val:MVtab2[code].val);
  }
#endif /* TRACE */

  return Get_Bits1() ? -MVtab2[code].val : MVtab2[code].val;
}

/* get differential motion vector (for dual prime prediction) */
int Get_dmvector()
{
#ifdef TRACE
  if (Trace_Flag)
    printf("dmvector (");
#endif /* TRACE */

  if (Get_Bits(1))
  {
#ifdef TRACE
    if (Trace_Flag)
      printf(Show_Bits(1) ? "11): -1\n" : "10): 1\n");
#endif /* TRACE */
    return Get_Bits(1) ? -1 : 1;
  }
  else
  {
#ifdef TRACE
    if (Trace_Flag)
      printf("0): 0\n");
#endif /* TRACE */
    return 0;
  }
}

int Get_coded_block_pattern()
{
  int code;

#ifdef TRACE
  if (Trace_Flag)
    printf("coded_block_pattern_420 (");
#endif /* TRACE */

  if ((code = Show_Bits(9))>=128)
  {
    code >>= 4;
    Flush_Buffer(CBPtab0[code].len);

#ifdef TRACE
    if (Trace_Flag)
    {
      Print_Bits(code,5,CBPtab0[code].len);
      printf("): ");
      Print_Bits(CBPtab0[code].val,6,6);
      printf(" (%d)\n",CBPtab0[code].val);
    }
#endif /* TRACE */

    return CBPtab0[code].val;
  }

  if (code>=8)
  {
    code >>= 1;
    Flush_Buffer(CBPtab1[code].len);

#ifdef TRACE
    if (Trace_Flag)
    {
      Print_Bits(code,8,CBPtab1[code].len);
      printf("): ");
      Print_Bits(CBPtab1[code].val,6,6);
      printf(" (%d)\n",CBPtab1[code].val);
    }
#endif /* TRACE */

    return CBPtab1[code].val;
  }

  if (code<1)
  {
    if (!Quiet_Flag)
      printf("Invalid coded_block_pattern code\n");
    Fault_Flag = 1;
    return 0;
  }

  Flush_Buffer(CBPtab2[code].len);

#ifdef TRACE
  if (Trace_Flag)
  {
    Print_Bits(code,9,CBPtab2[code].len);
    printf("): ");
    Print_Bits(CBPtab2[code].val,6,6);
    printf(" (%d)\n",CBPtab2[code].val);
  }
#endif /* TRACE */

  return CBPtab2[code].val;
}

int Get_macroblock_address_increment()
{
  int code, val;

#ifdef TRACE
  if (Trace_Flag)
    printf("macroblock_address_increment (");
#endif /* TRACE */

  val = 0;

  while ((code = Show_Bits(11))<24)
  {
    if (code!=15) /* if not macroblock_stuffing */
    {
      if (code==8) /* if macroblock_escape */
      {
#ifdef TRACE
        if (Trace_Flag)
          printf("00000001000 ");
#endif /* TRACE */

        val+= 33;
      }
      else
      {
        if (!Quiet_Flag)
          printf("Invalid macroblock_address_increment code\n");

        Fault_Flag = 1;
        return 1;
      }
    }
    else /* macroblock suffing */
    {
#ifdef TRACE
      if (Trace_Flag)
        printf("00000001111 ");
#endif /* TRACE */
    }

    Flush_Buffer(11);
  }

  /* macroblock_address_increment == 1 */
  /* ('1' is in the MSB position of the lookahead) */
  if (code>=1024)
  {
    Flush_Buffer(1);
#ifdef TRACE
    if (Trace_Flag)
      printf("1): %d\n",val+1);
#endif /* TRACE */
    return val + 1;
  }

  /* codes 00010 ... 011xx */
  if (code>=128)
  {
    /* remove leading zeros */
    code >>= 6;
    Flush_Buffer(MBAtab1[code].len);

#ifdef TRACE
    if (Trace_Flag)
    {
      Print_Bits(code,5,MBAtab1[code].len);
      printf("): %d\n",val+MBAtab1[code].val);
    }
#endif /* TRACE */

    
    return val + MBAtab1[code].val;
  }
  
  /* codes 00000011000 ... 0000111xxxx */
  code-= 24; /* remove common base */
  Flush_Buffer(MBAtab2[code].len);

#ifdef TRACE
  if (Trace_Flag)
  {
    Print_Bits(code+24,11,MBAtab2[code].len);
    printf("): %d\n",val+MBAtab2[code].val);
  }
#endif /* TRACE */

  return val + MBAtab2[code].val;
}

/* combined MPEG-1 and MPEG-2 stage. parse VLC and 
   perform dct_diff arithmetic.

   MPEG-1:  ISO/IEC 11172-2 section
   MPEG-2:  ISO/IEC 13818-2 section 7.2.1 
   
   Note: the arithmetic here is presented more elegantly than
   the spec, yet the results, dct_diff, are the same.
*/

int Get_Luma_DC_dct_diff()
{
  int code, size, dct_diff;

#ifdef TRACE
/*
  if (Trace_Flag)
    printf("dct_dc_size_luminance: (");
*/
#endif /* TRACE */

  /* decode length */
  code = Show_Bits(5);

  if (code<31)
  {
    size = DClumtab0[code].val;
    Flush_Buffer(DClumtab0[code].len);
#ifdef TRACE
/*
    if (Trace_Flag)
    {
      Print_Bits(code,5,DClumtab0[code].len);
      printf("): %d",size);
    }
*/
#endif /* TRACE */
  }
  else
  {
    code = Show_Bits(9) - 0x1f0;
    size = DClumtab1[code].val;
    Flush_Buffer(DClumtab1[code].len);

#ifdef TRACE
/*
    if (Trace_Flag)
    {
      Print_Bits(code+0x1f0,9,DClumtab1[code].len);
      printf("): %d",size);
    }
*/
#endif /* TRACE */
  }

#ifdef TRACE
/*
  if (Trace_Flag)
    printf(", dct_dc_differential (");
*/
#endif /* TRACE */

  if (size==0)
    dct_diff = 0;
  else
  {
    dct_diff = Get_Bits(size);
#ifdef TRACE
/*
    if (Trace_Flag)
      Print_Bits(dct_diff,size,size);
*/
#endif /* TRACE */
    if ((dct_diff & (1<<(size-1)))==0)
      dct_diff-= (1<<size) - 1;
  }

#ifdef TRACE
/*
  if (Trace_Flag)
    printf("): %d\n",dct_diff);
*/
#endif /* TRACE */

  return dct_diff;
}


int Get_Chroma_DC_dct_diff()
{
  int code, size, dct_diff;

#ifdef TRACE
/*
  if (Trace_Flag)
    printf("dct_dc_size_chrominance: (");
*/
#endif /* TRACE */

  /* decode length */
  code = Show_Bits(5);

  if (code<31)
  {
    size = DCchromtab0[code].val;
    Flush_Buffer(DCchromtab0[code].len);

#ifdef TRACE
/*
    if (Trace_Flag)
    {
      Print_Bits(code,5,DCchromtab0[code].len);
      printf("): %d",size);
    }
*/
#endif /* TRACE */
  }
  else
  {
    code = Show_Bits(10) - 0x3e0;
    size = DCchromtab1[code].val;
    Flush_Buffer(DCchromtab1[code].len);

#ifdef TRACE
/*
    if (Trace_Flag)
    {
      Print_Bits(code+0x3e0,10,DCchromtab1[code].len);
      printf("): %d",size);
    }
*/
#endif /* TRACE */
  }

#ifdef TRACE
/* 
  if (Trace_Flag)
    printf(", dct_dc_differential (");
*/
#endif /* TRACE */

  if (size==0)
    dct_diff = 0;
  else
  {
    dct_diff = Get_Bits(size);
#ifdef TRACE
/*
    if (Trace_Flag)
      Print_Bits(dct_diff,size,size);
*/
#endif /* TRACE */
    if ((dct_diff & (1<<(size-1)))==0)
      dct_diff-= (1<<size) - 1;
  }

#ifdef TRACE
/*
  if (Trace_Flag)
    printf("): %d\n",dct_diff);
*/
#endif /* TRACE */

  return dct_diff;
}